Hammer striking line

[Delwin D Fandrich]

Frank Weston wrote:
> 
> Dear List,
> 
> I am in the process of rebuilding a 1912 Knabe model B grand.  As this
> piano has had at least two hammer set replacements, and because many of
> the hammers on the last set were broken or missing, the determination of
> the factory ordained hammer striking line is impossible.
> 
> I have considered hanging a few trial hammers at 1/7 of the speaking
> length, and sliding the action in and out until I get the best sound,
> and then setting the striking line from that reference.  Is there a
> better or more efficient way to proceed?
>  
> P.S. To complicate matters further, this particular piano has very
> different action geometry from other Knabe B's which I have rebuilt.
> The hammer shanks (to fit in the treble) must be about 1/8 to 3/16 inch
> shorter than other Knabes and comparable sized grands of other makes.
> 
> Frank Weston

Frank,

Rarely, if ever, has 1/7 of the speaking length actually been used as a
real life hammer strike point. This ratio has its origins in some of
John Broadwood's work. Typically, a piano of that era (1912) will have a
strike point at approximately 1/12th to 1/16th of the striking point at
C-88. This will change more or less uniformly down through the scale and
end up somewhere around 1/8th in the lower third of the scale. From
there down the ratio will probably be somewhere between 1/7.5 to 1/8.5.
There are always exceptions, but this should provide a good starting
point.

If you have absolutely no idea where the original hammers were, but you
can get the action close to its original position, try the following:
  1)  With the new hammershanks in place (I assume you're going to use
new hammershanks), fit one of your new hammers to C-88. Through trial
and error locate that hammer to the correct strike point, i.e., fit for
best sound. You'll find that the point giving the best sound will
probably be about 3.5 mm behind the V-bar. Temporarily glue your sample
hammer in place--i.e., use just a tiny bit of glue. You can now measure
along the hammershank from the action center to the leading edge of the
hammer molding and use that dimension as a reference starting point for
all subsequent hammer positions. Mark this point on the end hammershanks
of each section with a pencil.
  2)  Move down the scale to the lowest hammershank in the top treble
section and do the same. You'll find that the best sounding point for
this hammer will not be more than a couple of mm from your pencil mark.
If it seems to be further off than this, try to find out why.
  3)  Do the same for the end hammers of the lower treble section.
  4)  Through the bass and tenor sections, the hammer position will
probably be the same as it was for C-88, but you will have to check the
end hammers of each section for tone and physical clearance to be sure. 

The above assumes that you always return the keyframe and action to the
same fore & aft position each time you make a sound check. Mark it at
both ends to be sure. It also assumes that you have drilled and reamed
the sample hammers for a snug fit and that they are exactly 90 degrees
to the hammershank. 

In real life, the exact hammer strike point on the string is not so
critical once you're out of the top two sections. Good thing, too. Many
scales--including some in current production--are all over the ball park
through both the bass and tenor sections and especially across the
bass/tenor break. 

Let me know if you have any trouble with this system. I've used it more
than once with good results.

ddf